The present invention relates generally to prostaglandin compositions. In particular, the present invention relates to storage stable, pharmaceutical compositions containing prostaglandins and surfactants. As used herein, the term "prostaglandin" or "PG" shall refer to prostaglandins and derivatives and analogues thereof including pharmaceutically acceptable salts and esters, except as otherwise indicated by context.
Prostaglandins have notoriously low water solubility, and are generally unstable. Attempts have been made to solubilize and stabilize various prostaglandins by complexing them with different cyclodextrins. See, for example: EP 330 511 A2 (Ueno et al.) and EP 435 682 A2 (Wheeler). These attempts have met with varying success.
Surfactants and/or solubilizers have been used with other types of drugs having low water solubility. However, the addition of surfactants and/or solubilizers may enhance or adversely affect the chemical stability of drug compounds. See Surfactant Systems, Their Chemistry, Pharmacy, and Biology, (eds. Attwood et al.), Chapman and Hall, New York, 1983, Ch. 11, particularly pp. 698-714.
The use of non-ionic surfactants, such as polyethoxylated castor oils, as solubilizing agents is known. See, for example, U.S. Pat. No. 4,960,799 (Nagy).
The use of non-ionic surfactants such as polyethoxylated castor oils in stable emulsions is also known. U.S. Pat. No. 4,075,333 (Josse) discloses stable, intravenous emulsion formulations of vitamins. El-Sayed et al., Int J. Pharm., 13:303-12 (1983) discloses stable oil-in-water emulsions of an antineoplastic drug. U.S. Pat. No. 5,185,372 (Ushio et al.) discloses topically administrable ophthalmic formulations of vitamin A which are stable preparations in which a non-ionic surfactant is used to form an emulsion of vitamin A in an aqueous medium.
What is needed is a commercially viable, storage-stable prostaglandin composition.